Foundry core blowing machines usually employ a single (one or a set of) clamp piston-cylinder assembly for assembling the cope and drag parts of the core box and for clamping the core box against the blow head and subsequently the cure or gassing head. Between the blow and cure, the box is actually unclamped.
Because of the blow operation the abutting core box parts (cope and drag) include a face seal. The seal exerts a force tending to separate the box parts. Also the blow operation creates what is known as "rebound" which again tends to open the cope and drag. When the sand resin mix is blown into the box it tends to be chilled by the blow operation. However, when it warms subsequently it tends to expand, again tending to open the box.
A box even slightly open at the parting line prior to cure creates on the core what is known as a fin. Initially only one or two grains of sand may get between the box parts at the parting line. However, the sand stays and as the machine cycle continues more and more sand enters between the box parts and the fin gets larger and larger with each subsequent core.
Finning results in loss of dimensional stability of the core and will eventually alter the dimension of the core to be out of spec. In fact, because of the problem core specifications are notoriously wide. Moreover, the sand abrades the edges of the tooling and creates excessive parting line wear. This in turn requires frequent repair or rebuilding of very expensive tooling. The problem also tends to create frequent cleaning and inspection during the operation of the machine which results in a slowing of the machine cycle or production rate.
Finning also causes subsequent inspection, modification or cleaning of the core itself, or even the casting made, all of which is extremely labor intensive. The problem is an anathema both to automation and accuracy. It would therefore be desirable to provide a high capacity automated and efficient machine which would minimize the finning problem. While it is desirable to reduce finning, it is also desirable to provide a fully automated machine which runs more continuously without tooling changes, but when such changes are required provides automatic quick change of tooling.